Moveable 26" Build Thread

[shuboyje]

Re: Moveable 26" Build Thread

More pictures...

Some thoughts so far...

- Even though casting in sections and using iced water.... it was still sometimes a challenge to get the work done before the castable concrete became unworkable.

Casting an oven with that wall thickness is pretty uncommon, so I would imagine the logistics of it all were a bit much to take on without commercial scale equipment. Generally cast ovens are 2" thick or so. My most recent one is actually only 1-1/4". You can see you were dealing with WAY more material. What you did is probably equivalent to casting a 48" oven.

[di11on]

Re: Moveable 26" Build Thread

Casting an oven with that wall thickness is pretty uncommon, so I would imagine the logistics of it all were a bit much to take on without commercial scale equipment. Generally cast ovens are 2" thick or so. My most recent one is actually only 1-1/4". You can see you were dealing with WAY more material. What you did is probably equivalent to casting a 48" oven.

Really? Someone had said 2.5 to 3" Mine should be around this on average. In addition, I was also going by the Panyol 66 which has the same internal diameter and a wall thickness of 4" plus they advise adding more thermal mass?

Anyway - it was challenging but I think it's turned out quite well in the end.

Some questions:

1. Do I need to use refractory mortar for the external layer of vermicrete or can I simply use portland?
2. Regarding curing and curing fires... as you can see from pictures above, I have had the sections of my dome with the inside facing the sun for a few days which should help with drying it out? I presume I should do the curing process (fires and controlled temperature rise over number of days etc.) before mortaring the sections together?

[david s]

Re: Moveable 26" Build Thread

1. Do I need to use refractory mortar for the external layer of vermicrete or can I simply use portland?
2. Regarding curing and curing fires... as you can see from pictures above, I have had the sections of my dome with the inside facing the sun for a few days which should help with drying it out? I presume I should do the curing process (fires and controlled temperature rise over number of days etc.) before mortaring the sections together?

You can use refractory mortar if you want to but it is more expensive and you don't really want to add any aggregate because that will reduce the insulation value of the mix. Portland is sufficient, but don't make it too rich because it also reduces the insulation value. I use a 10:1 mix ie 10 parts vermiculite to one part cement. This will make a reasonably workable mix. For every 10 parts vermiculite add around three parts water. I like to apply the stuff in layers around an inch and a half thick and allow it to dry for a week before doing the next layer. Then do the drying out fires.

[shuboyje]

Re: Moveable 26" Build Thread

If you are at 2.5 to 3 inches you are closer to the norm. Your castings look every bit the thickness of you firebricks which should be 4.5".

The mass of a masonry oven should be adjusted for it's use. If you want to do retained heat baking for days, or cook commercial amounts of bread, you want lots of mass. For a home oven most people want the opposite of this even if they don't realize it which means less mass. That is where castable shines. Where a brick dome needs a certain thickness to have structural stability, a castable dome can be as thin as the product allows. I hope all this put together helps explain my earlier comments a bit better.

[di11on]

Re: Moveable 26" Build Thread

Thanks Shuboyje.

Actually, my firebricks are 5cm (2") thick, so that might explain why the casting looks so thick in comparison?

[di11on]

Re: Moveable 26" Build Thread

So I have my arch set up, just needs some mortar :-)

[di11on]

Re: Moveable 26" Build Thread

You can use refractory mortar if you want to but it is more expensive and you don't really want to add any aggregate because that will reduce the insulation value of the mix. Portland is sufficient, but don't make it too rich because it also reduces the insulation value. I use a 10:1 mix ie 10 parts vermiculite to one part cement. This will make a reasonably workable mix. For every 10 parts vermiculite add around three parts water. I like to apply the stuff in layers around an inch and a half thick and allow it to dry for a week before doing the next layer. Then do the drying out fires.

Wouldn't it make sense to light some fires before I mortar the dome sections together... to avoid the risk of cracking and steam explosions?

[david s]

Re: Moveable 26" Build Thread

Wouldn't it make sense to light some fires before I mortar the dome sections together... to avoid the risk of cracking and steam explosions?

Cast sections are usually fired in place. If you dry the sections out completely the mortar is going to make the castings wet again around the joint anyway. Probably better to mortar them first and leave for a week before any fires.

[di11on]

Re: Moveable 26" Build Thread

Hi all,

Some more pictures of the build.

Here I've completed the arch. I've created a chimney by using half bricks for the top 5 bricks of the arch. I then created a smooth tapered chimney by using two of the cut bricks and angled them at around 45 degrees. Works quite nicely.

[di11on]

Re: Moveable 26" Build Thread

... just put on ceramic fibre blanket, chicken wire and outer layer of vermicrete.

I bought enough fibre blanket for one 1" layer but I got nearly two layers out of it. This did create some gaps. The wire mesh I got was too fine to allow the vermicrete to go through so I had to cut some holes here are there. However there are probably some airpockets where there is a gap between fibre blanket sections and the vermicrete... I hope this won't be too much of a problem?!

My brickmanship isn't great as you can see but it will have to do :-)

[david s]

Re: Moveable 26" Build Thread

... just put on ceramic fibre blanket, chicken wire and outer layer of vermicrete.

I bought enough fibre blanket for one 1" layer but I got nearly two layers out of it. This did create some gaps. The wire mesh I got was too fine to allow the vermicrete to go through so I had to cut some holes here are there. However there are probably some airpockets where there is a gap between fibre blanket sections and the vermicrete... I hope this won't be too much of a problem?!

My brickmanship isn't great as you can see but it will have to do :-)

Looks pretty nice to me, good job.

[di11on]

Re: Moveable 26" Build Thread

Hi folks,

Outer stucco layer and chimney in place. Oven door made :-)

I've had 4 pizza making sessions so far and the oven is working very nicely. No cracks in the dome at all. Heats up to temp in around 1.25 hours.

The only problem I'm having is that I seem to have messed up a bit with the chimney design. The chimney isn't insulated so the heat goes from the chimney back across the stucco layer and has made it crack going from the chimney back across the top of the stucco layer.

Anyone any suggestions about how to deal with this? I guess if I paint over it, it will just crack also? I could insulate the chimney by putting an isolated tube inside it, but then it would probably be too narrow? It's 10cm in diameter as it is.

[david s]

Re: Moveable 26" Build Thread

After several more firings fill the crack with acrylic render and coat the whole thing with the stuff to waterproof it. You can thin it with water and paint the stuff on.

[di11on]

I never did post a finished photo of the oven. Just used it yesterday evening and it's still working great. The acrylic render worked like a charm - thanks for the recommendation

[di11on]

Hi all,

As per the title - the idea behind this oven was that it could be moved eventually from our rented house to our next location. Well, we finally bought a house and the time came to move the oven... but how would we do it and would it survive the move?

Well with the help of a tractor called Classy, the wonderful people at Domaine Galus and a few strong arms - we managed to pull it off. With some expert manoeuvring in the confined area of our front garden, it was possible to lift the oven out, put it in a trailer and then pick it back up a the other end. Unfortunately, due to a low roof at the final destination - the final two or three meters required some ingenious improvisation using bricks, part of a swing set, some old window shutters and a good bit of heave-ho!

So - it did turn out to be moveable in the end.. but only just about. Six of us did try to manually lift it - but it was never gonna happen. So, 26 inches really was the biggest I could have gone for while still having some hope of ever moving it!

Here are some pics: